1. Field of the Invention
The present invention relates generally to artificial firelogs and particularly to artificial firelogs where the binder material includes non-petroleum derived waxes.
2. Description of the Related Art
Fireplaces have been used in homes over the years for providing heat as well as to provide a desired ambience. While wood and coal have been the primary fuels for burning in fireplaces, there is an increasing demand for manufactured or artificial fireplace logs. These logs are typically easier to purchase and store, provide better heating values (BTU/lb) than wood or coal, are easier to light, safer to use with virtually no maintenance during burning, and can be used to build fires of a known duration, generally from 2 hours to more than 4 hours.
Artificial firelogs are typically manufactured by combining a carrier material, usually particles of cellulosic origin, with a combustible binder/fuel. The cellulosic material may be sawdust, or a mixture of sawdust with other combustible materials of varying proportion. The binder/fuel typically consists of a suitable blend of waxes, typically a flammable wax such as paraffin or slack wax, flammable vegetable oils such as stearic and/or palmitic acid or other fatty acids or esters which can be used either alone or in combination with other combustible materials. Additives imparting desired combustion characteristics, appearance, and other attributes may be combined with the basic ingredients. Such additives may include chemicals designed to color or otherwise modify or retard the flame, add aroma or crackling sounds or otherwise change the burning characteristics to more closely mimic the burning of natural logs. Following thorough mixing of the ingredients, the resulting mixture is formed into suitable, log-like shapes by extrusion, molding or compression, in either a batch or continuous process.
U.S. Pat. Nos. 3,297,419; 6,017,373; 6,136,054; 5,868,804; 4,333,738; 4,326,854; 3,843,336; and 4,040,796, incorporated herein by reference in their entireties, provide examples of known artificial firelog compositions, configurations and methods of manufacture.
Firelog base waxes should have physical characteristics (e.g. melting point, hardness and/or malleability) that permit the material to be readily formed into firelogs having a pleasing appearance and/or feel to the touch, as well as having desirable olfactory properties.
Artificial firelogs are typically manufactured from blends of about 50% to about 60% (by weight) petroleum waxes and about 40% to 50% (by weight) cellulosic fibers. The petroleum wax constituent, which may include paraffin wax or slack wax by way of example, provides the principal fuel content for the firelog and contains about twice the BTU (British thermal unit) energy value per unit mass as the cellulosic fibers.
In recent years, there has been dramatic inflation in the cost of petroleum products, including refined products such as petroleum waxes. For example, petroleum wax costs increased 120% between January 2004 and July 2006, making it less economic for firelog manufacturers to use petroleum wax in their products. Furthermore, paraffin wax material is derived from non-renewable petroleum fossil fuel, and thus the byproducts of burning such fuel can contribute to the Greenhouse Effect.
The most common binder component of synthetic firelogs is a petroleum slack wax or a synthetic polymer of high molecular weight which provides good adhesion with cellulosic fibers. Saturated fatty acids such as palmitic or stearic acids can be used to raise the melting point of the wax blend or to solidify the binder. Unsaturated, oily fatty acids are generally excluded because they are liquid at room temperature and lack the binding characteristics required for firelogs. A liquid or soft wax binder material, such as that disclosed in U.S. Pat. No. 4,326,854, must be solidified with the fibers using chemical processes such as polymerization or neutralization in order to form a firelog, which can significantly increase the cost and complexity of production.
Therefore, there remains a need for renewable, non-petroleum based materials which can provide a clean burning base wax for forming firelogs in a practical, cost effective manner. If possible, such materials would preferably be biodegradable as well. Thus, an object of the present invention is to provide alternative raw materials for use in the manufacture of firelogs, materials that allow for the elimination or reduction in petroleum wax by substituting other, more cost effective, environmentally friendly and readily available materials that make up for the BTU energy content lost from the elimination or reduction of the higher BTU petroleum wax.